The present invention relates to a process for temperature control, and in particular to a process for the temperature control of a drying apparatus in which cut tobacco leaves charged into the entrance thereof are dried to a required moisture rate and from which the cut tobacco leaves are then discharged.
In drying cut tobacco leaves, manufacturers make every effort in order to obtain final tobacco products with a consistent required moisture rate. There are two consecutive periods of time in a drying process for cut tobacco leaves. One is the period of time shortly after cut tobacco leaves begin to be charged into the drying apparatus and this is called the rise-up time or unsteady period during which the flow rate of the cut tobacco leaves at the exit of the drying apparatus has not yet reached its steady value. The other time period is the period of time subsequent to the unsteady period and is called the stable time or the steady period during which the flow rate of the cut tobacco leaves at the exit of the drying apparatus has reached its steady value.
If the cut tobacco leaves are dried in the same manner throughout these two drying-periods, the cut tobacco leaves are over-dried in the unsteady period because of excess heat for the flow rate of the cut tobacco leaves in that period and it is impossible to obtain cut tobacco leaves having the desired moisture rate during the unsteady period.
For example, if the unsteady period of a drying apparatus is 10 to 15 minutes and the flow rate of the tobacco leaves is 6000 kg/h, then, it is easy to obtain an unqualified production of 50 to 100 kg.
Furthermore, recent customers' requirements for tobacco taste are high and it is required to provide not only just-qualified products but also products with high-quality.